Pliable plastic film and container using the same

ABSTRACT

A pliable plastic film according to the present invention comprises a heat sealable sealing layer, wherein the sealing layer is made of a mixture of a propylene-α-olefin random copolymer having a crystalline melting point T m  of 135 to 145° C. and a polypropylene (PP) homopolymer having a crystalline melting point T m  of higher than 160° C.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pliable plastic film which canmaintain a function of an easily releasable sealed portion even after asterilization treatment at a high temperature of higher than 120° C.,and a container using the same.

2. Description of the Related Art

Recently, a multichamber container, which separately contains aplurality of components and is capable of mixing the components in thecontainer when used, is used in the medical field such as infusionsolution bag.

The multichamber container comprises a plastic container havingpliability, and a plurality of chambers which are partitioned with aso-called easily releasable sealed portion, and the seal strength of theeasily releasable sealed portion is adjusted so that the easilyreleasable sealed portion is released when a pressure is applied bypressing the chamber.

The easily releasable sealed portion is usually formed by heat sealedfilms made of a mixture of two or more kinds of resins which areinferior in compatibility and have different melting points. A containerused in the medical field such as an infusion solution bag is formed byusing a resin mixture of polyethylene and polypropylene which haveestablished safety to the human body and stability to medicines (see,for example, Japanese Patent No. 2,675,075).

However, in a medical container containing hyperalimentation solution,peritoneal dialysis fluid, perfusate, irrigation water for surgicaloperation or the like, sterilization at a high temperature of 120° C. orhigher is sometimes required. In such a case, a sterilization treatmenttemperature exceeds a melting point of polyethylene, and there ariseproblems such as deformation of the container and increase in the peelstrength of the easily releasable sealed portion as a result of thesterilization treatment.

On the other hand, Japanese Unexamined Patent Publication No. 2000-5276proposes a multichamber container in which an innermost layerconstituting the easily releasable sealed portion of the container isformed of a mixture of a syndiotactic polypropylene having a crystallinemelting point T_(m) of 121 to 140° C. and polypropylene having anisotactic pentad fraction of 0.96 or less and a crystalline meltingpoint T_(m) of 140 to 160° C. for the purpose of maintaining thefunction of the easily releasable sealed portion even if a sterilizationtreatment is carried out at 120° C. or higher.

SUMMARY OF THE INVENTION

However, like the above medical container, even if the innermost layerof the container is formed of a mixture of two kinds of polypropyleneshaving different crystalline melting points T_(m), when the crystallinemelting point T_(m) of polypropylene having a higher crystalline meltingpoint T_(m) is 160° C. or lower, there is such a problem that anallowable range of a heat sealing temperature, at which an easilyreleasable seal can be formed, becomes very narrow as 1° C., as isapparent from Examples described later. Therefore, there is a problemthat it becomes necessary to strictly control the heat sealingtemperature to form an easily releasable seal and production processesbecome complicated. Further, there is a problem that easy releasabilityof the easily releasable seal deteriorates by a slight change of theheat sealing temperature and therefore the yield of the productdecreases.

Moreover, the above medical container is not sufficient in heatresistance and blocking may occur by carrying out a sterilizationtreatment at a high temperature.

Thus, an object of the present invention is to provide a pliable plasticfilm which is excellent in heat resistance and has a wide allowablerange of a heat sealing temperature at which an easily releasable sealcan be formed, and to provide a container using the same.

A pliable plastic film according to the present invention comprises aheat sealable sealing layer, wherein the sealing layer is made of amixture of a propylene-α-olefin random copolymer having a crystallinemelting point T_(m) of 135 to 145° C. and a polypropylene homopolymerhaving a crystalline melting point T_(m) of higher than 160° C.

Further, in the pliable plastic film according to the present invention,the content ratio of the polypropylene homopolymer is preferably from 5to 30% by weight based on the mixture.

In the pliable plastic film according to the present invention, it ispreferable that the polypropylene homopolymer has a melting point ofmore than 160° C. and not more than 170° C. and an isotactic pentadfraction of not less than 0.97.

It is preferable that the pliable plastic film according to the presentinvention further comprises a layer containing polypropylene formed onthe surface of the sealing layer.

It is preferable that the pliable plastic film according to the presentinvention further comprises a first flexible layer formed on the surfaceof the sealing layer, a reinforcing layer formed on the surface of thefirst flexible layer, a second flexible layer formed on the surface ofthe reinforcing layer, and an outermost layer formed on the surface ofthe second flexible layer, wherein

the first flexible layer is made of a mixture of at least one kind ofpolymer selected from the group consisting of a propylene-α-olefinrandom copolymer, a propylene-α-olefin block copolymer and asyndiotactic polypropylene, and an ethylene-α-olefin copolymerelastomer, and the content ratio of the ethylene-α-olefin copolymerelastomer is from 30 to 50% by weight based on the entire first flexiblelayer,

the reinforcing layer is made of at least one kind of polymer selectedfrom the group consisting of a polypropylene homopolymer, apropylene-α-olefin random copolymer, a propylene-α-olefin blockcopolymer and a cyclo olefin polymer,

the second flexible layer is made of a mixture of at least one kind ofpolymer selected from the group consisting of a propylene-α-olefinrandom copolymer, a propylene-α-olefin block copolymer and asyndiotactic polypropylene, and an ethylene-α-olefin copolymerelastomer, and the content ratio of the ethylene-α-olefin copolymerelastomer is from 30 to 50% by weight based on the entire secondflexible layer, and

the outermost layer is made of at least one kind of polymer selectedfrom the group consisting of a polypropylene homopolymer, apropylene-α-olefin random copolymer and a propylene-α-olefin blockcopolymer.

In the pliable plastic film according to the present invention, it ispreferable that the thickness of the first flexible layer and that ofthe second flexible layer respectively account for 30 to 40% of theentire film thickness.

A container according to the present invention comprises a heat sealablesealing layer, the sealing layer being made of a mixture of apropylene-α-olefin random copolymer having a crystalline melting pointT_(m) of 135 to 145° C. and a polypropylene homopolymer having acrystalline melting point T_(m) of higher than 160° C.,

the container being provided with a sealed portion formed by heatsealing the peripheral portions of the pliable plastic films in thestate where the sealing layers thereof face with each other.

The container according to the present invention is preferably providedwith an easily releasable sealed portion having a smaller peel strengththan that of the sealed portion, and is also provided with a pluralityof chambers partitioned with the sealed portion and the easilyreleasable sealed portion.

In the container according to the present invention, it is preferablethat the easily releasable sealed portion is heat sealed at atemperature which is higher than a crystalline melting point T_(m) ofthe propylene-α-olefin random copolymer having a crystalline meltingpoint T_(m) of 135 to 145° C. and is lower than a crystalline meltingpoint T_(m) of the polypropylene homopolymer having a crystallinemelting point T_(m) of higher than 160° C.

The container according to the present invention is preferably subjectedto a sterilization treatment at 121° C.

In the present invention, a crystalline melting point T_(m) means amelting peak temperature T_(pm) determined by differential scanningcalorimetry (DSC) (see Japanese Industrial Standard (JIS) K 7121).

In the present invention, “isotactic pentad fraction” means theproportion in which five propylene units are isotactically bondedcontinuously in a polymer of propylene (content ratio of mmmm structure;%). This isotactic pentad fraction is calculated as the sum of threeheptad fractions of m(mmmm)m, m(mmmm)r and r(mmmm)r based on assignmentof a peak of ¹³C-NMR spectrum for polypropylene.

According to the pliable plastic film of the present invention, when acontainer such as infusion solution bag is formed, the resultingcontainer can be excellent in heat resistance. Even if a containerprovided with the easily releasable sealed portion is formed using thepliable plastic film of the present invention and this container issubjected to, for example, a sterilization treatment at a hightemperature of 120° C. or higher, easy releasability of an easilyreleasable seal does not deteriorate. Moreover, when the easilyreleasable sealed portion is formed using the pliable plastic film ofthe present invention, it is possible to obtain a temperature range(allowable range), which is significant for industrial production, of aheat sealing temperature at which the easily releasable sealed portionis formed.

Therefore, the pliable plastic film of the present invention and thecontainer using the same are useful in a medical container whichrequires a steam sterilization treatment at a high temperature,particularly a multichamber container having an easily releasable seal.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a front view showing an embodiment of a container of thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

A pliable plastic film of the present invention comprises a heatsealable sealing layer, and this sealing layer is made of a mixture of apropylene-α-olefin random copolymer having a crystalline melting pointT_(m) of 135 to 145° C. and a polypropylene homopolymer having acrystalline melting point T_(m) of higher than 160° C.

The melting point of the propylene-α-olefin random copolymer having amelting point of 135 to 145° C., which constitutes a sealing layer, ispreferably from 136 to 140° C., and more preferably from 137 to 139° C.

When the melting point of the propylene-α-olefin random copolymerconstituting the sealing layer is lower than 135° C., heat resistance ofthe pliable plastic film and the container using the same deterioratesand blocking is likely to occur. On the other hand, when the meltingpoint of the propylene-α-olefin random copolymer constituting thesealing layer is higher than 145° C., the sealing temperature rangewhere the easily releasable sealed portion can be formed becomes narrow,and industrial productivity of the container provided with the easilyreleasable sealed portion is lowered. Further, when the melting point ofthe propylene-α-olefin random copolymer constituting the sealing layeris higher than 145° C., flexibility of the pliable plastic film and thecontainer using the same deteriorates.

Examples of the α-olefin in the propylene-α-olefin random copolymer ofthe propylene-α-olefin random copolymer having a melting point of 135 to145° C. include ethylene, or an α-olefin having 4 to 6 carbon atoms suchas 1-butene, 1-pentene, 1-hexene or 4-methyl-1-pentene.

In the propylene-α-olefin random copolymer, the content ratio of theα-olefin is not specifically limited, but is preferably from 1 to 5% byweight. With respect to the propylene-α-olefin random copolymer, theranges of the molecular weight, polymerization degree, molecular weightdistribution and the like are not specifically limited and can beappropriately selected within a range where the melting point can be setwithin the above range.

The propylene-α-olefin random copolymer is preferably apropylene-ethylene random copolymer in which the content ratio ofethylene is from 1 to 3% by weight.

The melting point of the polypropylene homopolymer having a meltingpoint of higher than 160° C., which constitutes the sealing layer, ispreferably higher than 160° C. and not more than 170° C., and morepreferably from 161 to 165° C.

When the melting point of the polypropylene homopolymer constituting thesealing layer is 160° C. or lower, the sealing temperature range wherethe easily releasable sealed portion can be formed becomes narrow, andindustrial productivity of the container provided with the easilyreleasable sealed portion is lowered. On the other hand, although theupper limit of the melting point of the propylene-α-olefin randomcopolymer constituting the sealing layer is not specifically limited,flexibility of the pliable plastic film may deteriorate when the meltingpoint is higher than 170° C.

In the polypropylene homopolymer of the polypropylene homopolymer havinga melting point of higher than 160° C., an isotactic pentad fraction ispreferably 0.97 or more. The polypropylene having an isotactic pentadfraction of 0.97 or more has very high stereoregularity and high meltingpoint. On the other hand, in polypropylene having an isotactic pentadfraction of less than 0.97, one having a melting point of higher than160° C. is less.

With respect to the polypropylene homopolymer, the ranges of themolecular weight, polymerization degree, molecular weight distributionand the like are not specifically limited and can be appropriatelyselected within a range where the melting point can be set within theabove range.

In the mixture of the propylene-α-olefin random copolymer having amelting point of 135 to 145° C. and the polypropylene homopolymer havinga melting point of higher than 160° C. which constitutes the sealinglayer, the content ratio of the polypropylene homopolymer in the mixtureis preferably from 5 to 30% by weight, and more preferably from 10 to20% by weight. When the content ratio of the polypropylene homopolymerhaving a melting point of higher than 160° C. is more than 30% by weightbased on the mixture, flexibility of the pliable plastic film and thecontainer using the same may deteriorate. On the other hand, when thecontent ratio of the polypropylene homopolymer having a melting point ofhigher than 160° C. is less than 5% by weight based on the mixture, easyreleasability of the pliable plastic film may deteriorate and also theallowable range of the heat sealing temperature, where the easilyreleasable sealed portion can be formed, may become narrow.

Examples of the pliable plastic film of the present invention include:

(a) a single-layered film composed only of a sealing layer; and(b) a multi-layered film comprising the sealing layer, and a layercontaining polypropylene formed on the surface of the sealing layer.

When the pliable plastic film of the present invention is thesingle-layered film in (a), the thickness of the film is notspecifically limited as far as pliability and flexibility required forthe film can be maintained, but is preferably from 150 to 350 μm, andmore preferably from 200 to 300 μm.

The single-layered film in (a) can be formed by mixing thepropylene-α-olefin random copolymer having the crystalline melting pointT_(m) of 135 to 145° C. with the polypropylene homopolymer having thecrystalline melting point T_(m) of higher than 160° C., and molding thesealing layer by a known molding method such as T-die extrusion moldingmethod or inflation molding method.

In any of the above molding methods, molding must be performed at atemperature at which the mixture of the propylene-α-olefin randomcopolymer having the crystalline melting point T_(m) of 135 to 145° C.and the polypropylene homopolymer having the crystalline melting pointT_(m) of higher than 160° C. is melted. However, when the moldingtemperature is too high, a part of a plastic may cause heatdeterioration. Therefore, the molding temperature of the single-layeredfilm is preferably from 200 to 230° C., but is not limited to thisrange.

When the pliable plastic film of the present invention is themulti-layered film in (b), its specific layer configuration includes:

(i) a multi-layered film comprising the sealing layer, a first flexiblelayer formed on the surface of the sealing layer, and an outermost layerformed on the surface of the first flexible layer; and(ii) a multi-layered film comprising the sealing layer, a first flexiblelayer formed on the surface of the sealing layer, a reinforcing layerformed on the surface of the first flexible layer, a second flexiblelayer formed on the surface of the reinforcing layer, and an outermostlayer formed on the surface of the second flexible layer.

When the pliable plastic film of the present invention is themulti-layered film, the other film constituting the multi-layered filmis not specifically limited, except that it is a film having heatresistance which can endure a sterilization treatment, and can beappropriately selected from films made of thermoplastic plastics such aspolyolefin, cyclo olefin polymer, polyester and polyamide.

Examples of the polyolefin include homopolyethylene, ethylene-α-olefincopolymer, polypropylene homopolymer, propylene-α-olefin randomcopolymer and propylene-α-olefin block copolymer.

Examples of the α-olefin of the ethylene-α-olefin copolymer includeα-olefins having 3 to 6 carbon atoms, such as propylene, 1-butene,1-pentene, 1-hexene and 4-methyl-1-pentene.

Examples of the α-olefin of the propylene-α-olefin random copolymer andthe propylene-α-olefin block copolymer include ethylene, and an α-olefinhaving 4 to 6 carbon atoms such as 1-butene, 1-pentene, 1-hexene or4-methyl-1-pentene.

Examples of the cyclo olefin polymer include cyclo olefin polymer suchas copolymer (or a hydrogenated product thereof) of ethylene and adicyclopentadiene-based compound, copolymer (or a hydrogenated productthereof) of ethylene and a norbornene-based compound, ring-openingpolymer (or a hydrogenated product thereof) of a cyclopentadiene-basedcompound, and ring-opening copolymer (or a hydrogenated compoundthereof) composed of two or more kinds of cyclopentadiene-basedcompounds.

Examples of the polyester include polyethylene terephthalate (PET) andpolybutylene terephthalate (PBT).

Examples of the polyamide include nylons such as nylon-6, nylon-6,6 andnylon-6,10.

The other plastic film is preferably a polyolefin film in view ofcompatibility with the sealing layer and ease of a lamination treatment,and is particularly preferably polypropylene.

When the pliable plastic film of the present invention is themulti-layered film, the total thickness thereof is not specificallylimited as far as pliability and flexibility of the film can bemaintained, but is preferably from 150 to 350 μm, and more preferablyfrom 200 to 300 μm.

When the pliable plastic film of the present invention is themulti-layered film, the thickness of the sealing layer is notspecifically limited, but is preferably from 20 to 100 μm, and morepreferably from 30 to 50 μm, in view of ensuring heat resistance andstrength of the heat sealed peripheral portion and the easily releasablesealed portion.

The first flexible layer and second flexible layer (hereinafter, bothlayers are merely collectively referred to as a “flexible layer”,sometimes) are layers for the purpose of imparting flexibility to theentire film without adversely affecting heat resistance of themulti-layered film.

The flexible layer is, for example, a flexible layer made of a mixtureof at least one kind of polymer selected from the group consisting of apropylene-α-olefin random copolymer, a propylene-α-olefin blockcopolymer and a syndiotactic polypropylene, and an ethylene-α-olefincopolymer elastomer, the content ratio of the ethylene-α-olefincopolymer elastomer being from 30 to 50% by weight based on the entireflexible layer. The flexible layer is preferably a flexible layer madeof a mixture of a propylene-α-olefin random copolymer and anethylene-α-olefin copolymer elastomer, the content ratio of theethylene-α-olefin copolymer elastomer being form 30 to 50% by weightbased on the total amount of the propylene-α-olefin random copolymer andthe ethylene-α-olefin copolymer elastomer, and more preferably aflexible layer made of a mixture of a propylene-α-ethylene randomcopolymer and an ethylene-α-olefin copolymer elastomer, the contentratio of the ethylene-α-olefin copolymer elastomer being from 30 to 50%by weight based on the total amount of the propylene-α-olefin randomcopolymer and the ethylene-α-olefin copolymer elastomer.

The α-olefin in the propylene-α-olefin random copolymer and thepropylene-α-olefin block copolymer, which constitute the flexible layer,is the same α-olefin as that in the propylene-α-olefin random copolymerhaving a melting point of 135 to 145° C., which constitutes the sealinglayer, and is preferably ethylene.

Examples of the syndiotactic polypropylene constituting the flexiblelayer include polypropylene synthesized using a metallocene catalyst.

With respect to the propylene-α-olefin random copolymer,propylene-α-olefin block copolymer and syndiotactic polypropylene,although the ranges of the melting point, molecular weight,polymerization degree, molecular weight distribution and the likethereof are not specifically limited, the melting point is preferablyfrom about 135 to 145° C. in view of ensuring flexibility of theflexible layer.

The α-olefin in the ethylene-α-olefin copolymer elastomer constitutingthe flexible layer includes, for example, an α-olefin having 3 to 6carbon atoms such as propylene, 1-butene, 1-pentene, 1-hexene or4-methyl-1-pentene, and is preferably 1-butene.

The ethylene-α-olefin copolymer elastomer is not specifically limitedbut the density is preferably from 0.880 to 0.910 g/cm³.

The mixture of at least one kind of polymer selected from the groupconsisting of a propylene-α-olefin random copolymer, apropylene-α-olefin block copolymer and a syndiotactic polypropylene, andan ethylene-α-olefin copolymer elastomer, which constitutes the flexiblelayer, can be appropriately mixed with a styrene-based thermoplasticelastomer, a polypropylene homopolymer having a melting point of higherthan 160° C., and process oil in view of adjustment of flexibility ofthe film.

Examples of the styrene-based thermoplastic elastomer include astyrene-ethylene/butylene-styrene block copolymer (SEBS), astyrene-butadiene-styrene block copolymer (SBS), astyrene-isoprene-styrene block copolymer (SIS), a modified SEBS modifiedwith maleic acid, a styrene-ethylene/propylene-styrene block copolymer(SEPS), a styrene-ethylene/butylene block copolymer (SEB) and astyrene-ethylene/propylene block copolymer (SEP).

Examples of the polypropylene homopolymer having a melting point ofhigher than 160° C. include the same polypropylene homopolymer as thepolypropylene homopolymer having a melting point of higher than 160° C.,which constitutes the sealing layer.

The content ratio of the styrene-based thermoplastic elastomer or thepolypropylene homopolymer based on the mixture of at least one kind ofpolymer selected from the group consisting of a propylene-α-olefinrandom copolymer, a propylene-α-olefin block copolymer and asyndiotactic polypropylene, and an ethylene-α-olefin copolymerelastomer, which constitutes the flexible layer, is not specificallylimited, but the content ratio of the styrene-based thermoplasticelastomer or the polypropylene homopolymer based on the total amount ofthe mixture is preferably from 10 to 30% by weight.

Examples of the process oil include paraffinic process oil (manufacturedby Idemitsu Kosan Co., Ltd. under the trade name of “PW-90”, “PW-380”,and “PS-90”, etc.) and olefinic process oil (manufactured by MatsumuraOil Co., Ltd. under the trade name of “P18”, “P380”, “P46”, etc.).

The content ratio of the process oil based on the mixture of at leastone kind of polymer selected from the group consisting of apropylene-α-olefin random copolymer, a propylene-α-olefin blockcopolymer and a syndiotactic polypropylene, and an ethylene-α-olefincopolymer elastomer, which constitutes the flexible layer, is notspecifically limited, but can be appropriately set within a range wherea phenomenon of oozing of the process oil on the surface of a pliableplastic film can be prevented.

When the pliable plastic film of the present invention is themulti-layered film, the thickness of the flexible layer is notspecifically limited, but is preferably from 60 to 80% based on theentire film thickness.

The reinforcing layer is a layer formed for the purpose of preventinggeneration of defective products as a result of softening or flow of theflexible layer, for example, due to a sterilization treatment at a hightemperature.

Examples of the reinforcing layer include those made of at least onekind of polymer selected from the group consisting of a polypropylenehomopolymer, a propylene-α-olefin random copolymer, a propylene-α-olefinblock copolymer and a cyclo olefin polymer.

Examples of the polypropylene homopolymer constituting the reinforcinglayer include a polypropylene homopolymer having a melting point ofhigher than 160° C., which constitutes the sealing layer.

The α-olefin in the propylene-α-olefin random copolymer and thepropylene-α-olefin block copolymer, which constitute the reinforcinglayer, is the same α-olefin as in the propylene-α-olefin randomcopolymer having a melting point of 135 to 145° C., which constitutesthe sealing layer, and preferably ethylene.

Examples of the cyclo olefin polymer include the same cyclo olefinpolymer as those described above. The cyclo olefin polymer whose glasstransition temperature is from 100 to 170° C. is preferable, although itis not limited thereto.

When maintenance of flexibility of the pliable plastic film isconsidered to be important, the propylene-α-olefin random copolymerhaving a melting point of 135 to 145° C. is preferably used for thereinforcing layer. On the other hand, when the film strength and heatresistance of the pliable plastic film are considered to be important, apolypropylene homopolymer having a melting point of higher than 160° C.or a cyclo olefin polymer is preferably used as the material of thereinforcing layer.

The thickness of the reinforcing layer is not specifically limited, butpreferably from 3 to 15% based on the entire pliable plastic filmthickness.

The outermost layer is a layer formed for the purpose of preventinggeneration of defective products as a result of softening or flow of theflexible layer, for example, due to a sterilization treatment at a hightemperature.

Examples of the outermost layer include those made of at least one kindof polymer selected from the group consisting of a polypropylenehomopolymer, a propylene-α-olefin random copolymer and apropylene-α-olefin block copolymer.

Examples of the polypropylene homopolymer constituting the outermostlayer include a polypropylene homopolymer having a melting point ofhigher than 160° C., which constitutes the sealing layer.

The α-olefin in the propylene-α-olefin random copolymer and thepropylene-α-olefin block copolymer, which constitute the reinforcinglayer, is the same α-olefin as in the propylene-α-olefin randomcopolymer having a melting point of 135 to 145° C., which constitutesthe sealing layer, and preferably ethylene.

The composition of the plastic film constituting the outermost layer canbe appropriately decided in light of the strength, heat resistance,flexibility and the like of the entire pliable plastic film.

The multi-layered film can be produced by molding the sealing layer, thefirst flexible layer and the reinforcing layer, or the sealing layer,the first flexible layer, the reinforcing layer, the second flexiblelayer and the outermost layer through a known extrusion laminationmethod such as T-die coextrusion molding method or multilayer inflationmolding method, and laminating the resulting layers.

In any of the above-mentioned molding methods, molding must be performedat the temperature at which a plastic constituting each layer is melted.However, when the molding temperature is too high, a part of the plasticmay cause heat deterioration. Therefore, the molding temperature of themulti-layered film is preferably from 200 to 230° C., although it is notlimited thereto.

According to the pliable plastic film of the present invention,excellent heat resistance can be imparted to a container such as aninfusion solution bag formed using this pliable plastic film. When thecontainer is provided with an easily releasable sealed portion, easyreleasability of an easily releasable seal can be maintained even if thecontainer is subjected to a sterilization treatment at a hightemperature. Moreover, when the easily releasable sealed portion isformed in the container such as an infusion solution bag by using thispliable plastic film, it is possible to obtain a temperature range(allowable range), which is significant for industrial production, of aheat sealing temperature at which the easily releasable sealed portionis formed.

Therefore, the pliable plastic film of the present invention is suitedfor use as a material constituting the container such as an infusionsolution bag, particularly a material constituting a medical containerwhich requires a sterilization treatment at a high temperature such assteam sterilization treatment or hot water sterilization treatment.

As shown in FIG. 1, for example, the container 10 of the presentinvention is provided with a sealed portion 12 formed by heat sealingthe peripheral portions of the pliable plastic films in the state ofbeing laid one upon another so that the sealing layers thereof face witheach other.

Specifically, the container can be produced by the following procedure:

Two single-layered films extrusion-molded by a T-die method are laid oneupon another and peripheral portions thereof are heat sealed to form asealed portion, followed by molding into a bag or a tube.

The two multi-layered films coextrusion-molded by a T-die method arelaid one upon another so that sealing layers thereof face each other,and peripheral portions thereof are heat sealed to form a sealedportion, followed by molding into a bag or a tube.

The single-layered film inflation-molded is folded back on itself and aperipheral portion thereof is heat sealed to form a sealed portion,followed by molding into a bag or a tube.

The multi-layered film molded in a state where a sealed layer is formedinside is folded back on itself and a peripheral portion thereof is heatsealed to form a sealed portion, followed by molding into a bag or atube.

Heat sealing of the peripheral portion is conducted under the conditionsof a temperature of 170° C. or higher, and preferably from 180 to 200°C., for about 3 to 5 seconds, although the conditions are not limitedthereto.

When the container is provided with an easily releasable seal, a heatsealing temperature, at which an easily releasable seal is provided, isset to a temperature which is higher than a melting point of thepropylene-α-olefin random copolymer having a melting point of 135 to145° C. and is lower than a melting point of the polypropylenehomopolymer having a melting point of higher than 160° C.

Heat sealing conditions in case of forming an easily releasable seal areappropriately set so that the peel strength of the easily releasableseal can be set within a range from 3.92 to 5.88 N/15 mm (about 0.4 to0.6 kgf/15 mm) even after the container is subjected to a sterilizationtreatment at 121° C. Specifically, heat sealing is preferably conductedunder the conditions of a temperature of 140 to 155° C., more preferablyfrom 140 to 145° C., for about 4 to 5 seconds.

The peel strength is measured in accordance with the method described inJIS Z 0237 “Testing methods of pressure-sensitive adhesive tapes andsheets” (180° peel method). This peel strength is measured by cutting apliable plastic film from the easily releasable sealed portion as astarting point at a width of 15 mm, pulling a pair of film portions ofthe measured sample thus obtained at an angle of 180° and a speed of 200mm/min and measuring the strength (N/15 mm) when the easily releasableseal is peeled off.

As described above, the container of the present invention is formedusing the pliable plastic film of the present invention. Therefore, thecontainer of the present invention can be subjected to, for example, asterilization treatment at a high temperature, specifically, steamsterilization treatment or hot water sterilization treatment, forexample, at a temperature within a range from 100 to 121° C., andpreferably from 106 to 121° C. Even after subjecting to thesterilization treatment, easy releasabilty can be maintained in theeasily releasable sealed portion of the container of the presentinvention.

The container of the present invention is excellent in heat resistanceand, for example, even if the container provided with an easilyreleasable sealed portion is subjected to a sterilization treatment at ahigh temperature, easy releasability of the easily releasable seal canbe maintained. When the container of the present invention is providedwith an easily releasable sealed portion, it is possible to impart atemperature range (allowable range), which is significant for industrialproduction, to a heat sealing temperature at which the easily releasablesealed portion is formed. Thus, the manufacturing conditions for thecontainer are advantageous.

Therefore, the container of the present invention is useful in a medicalcontainer such as infusion solution bag, which requires, for example, asteam sterilization treatment at a high temperature, particularly amultichamber container having an easily releasable seal.

EXAMPLES

The present invention will now be described in more detail by way ofExamples and Comparative Examples, but the present invention is notlimited thereto.

Abbreviations, physical properties, manufacturers and trade names offilm forming materials used in the following Examples and ComparativeExamples are shown below.

PP1: Polypropylene-α-olefin random copolymer (crystalline melting pointT_(m): 138° C., manufactured by Mitsui Chemicals, Inc. under the tradename of “Mitsui POLYPRO F327”)PP2: Polypropylene homopolymer(crystalline melting point T_(m): 163° C.,isotactic pentad fraction 0.97, manufactured by Mitsui Chemicals, Inc.under the trade name of “Mitsui POLYPRO J103”)PP3: Polypropylene-α-olefin random copolymer (crystalline melting pointT_(m): 130° C., manufactured by Mitsui Chemicals, Inc. under the tradename of “Mitsui POLYPRO F337”)PP4: Polypropylene homopolymer (crystalline melting point T_(m): 160°C., isotactic pentad fraction 0.96, manufactured by Mitsui Chemicals,Inc. under the trade name of “Mitsui POLYPRO F107”)COP: Hydrogenated ring-opening polymer of norbornene-based monomer(specific gravity: 1.01, glass transition temperature: 105° C.,manufactured by ZEON Corporation “ZEONOR® 1020R”)PEE: Ethylene-1-butene copolymer (density: 0.885 g/cm³, manufactured byMitsui Chemicals, Inc. “TAFMER® A0585X”)

Example 1 and Comparative Examples 1 to 3

Pliable plastic films having the layer configuration shown in Table 1below were produced and also containers (infusion solution bag) 10 shownin FIG. 1 were produced using the films.

The pliable plastic films produced in Example 1 and Comparative Examples1 to 3 were obtained by laminating five layers of a sealing layer, afirst flexible layer, a reinforcing layer, a second flexible layer andan outermost layer in this order from one surface, and the thickness ofeach layer was set to 30 μm, 90 μm, 20 μm, 90 μm and 20 μm in this orderfrom the sealing layer.

The pliable plastic films were formed as an inflation film comprising asealing layer as an inner layer by a multilayer inflation method.

TABLE 1 Upper columns: Kinds of plastics constituting layers Lowercolumns: Mixing ratios (weight ratios) of plastics First Rein- SecondOuter- Sealing flexible forcing flexible most layer layer layer layerlayer (30 μm) (90 μm) (20 μm) (90 μm) (20 μm) Example 1 PP1 + PP2 PP1 +PEE PP1 PP1 + PEE PP1 (85:15) (60:40) (60:40) Comparative PP3 + PP2PP1 + PEE PP1 PP1 + PEE PP1 Example 1 (85:15) (60:40) (60:40)Comparative PP3 + PP4 PP1 + PEE PP1 PP1 + PEE PP1 Example 2 (85:15)(60:40) (60:40) Comparative PP1 + PP4 PP1 + PEE PP1 PP1 + PEE PP1Example 3 (85:15) (60:40) (60:40)

The inflation film having the layer configuration shown in Table 1 wascut into a predetermined length and the peripheral portion was heatsealed at 195° C. for 5 seconds to form a sealed portion 12, thusobtaining a container(infusion solution bag) 10 having pliability (seeFIG. 1).

In this container 10, the intermediate portion of a chamber 13 was heatsealed at 140 to 145° C. for 4.5 seconds to form an easily releasablesealed portion 11.

The easily releasable sealed portion 11 was formed by varying thesealing temperature in the respective Examples and Comparative Examples.Specifically, the sealing temperature was varied at a pitch of 0.1° C.within a range from 122 to 152° C.

As a port member 14 of the container 10, a port type port membercomprising an outer frame made of polyethylene and a plug body made of astyrene-based thermoplastic elastomer was used.

An upper chamber 13 a of the container was filled with 720 mL ofphysiological saline and a lower chamber 13 b was filled with 1,280 mLof physiological brine, followed by sealing and further high-pressuresteam sterilization at 121° C. for 20 minutes. A peel strength (N/15 mm,JIS Z 0237) of the easily releasable seal 11 after being subjected tothe sterilization treatment was measured using an autograph manufacturedby Shimadzu Corporation.

As a result of the measurement, the temperature range (° C.) of heatsealing, at which the peel strength of the easily releasable seal couldbe maintained within a range from 3.92 to 5.88 N/15 mm even after thesterilization treatment, and an allowable temperature (° C.) indicatedby the temperature range were determined.

The above results are shown in Table 2.

TABLE 2 Heat sealing temperature range Allowable temperature Example 1143.0 to 145.0° C. 2.0° C. Comparative Example 1 — — Comparative Example2 — — Comparative Example 3 131.0 to 132.0° C. 1.0° C.

As shown in Table 2, in all the containers made of the pliable plasticfilm of Example 1, allowable sealing temperature ranges of the easilyreleasable seal were 2° C. or more.

On the other hand, in the pliable plastic film of Comparative Example 3,a sealing temperature was within a range from 131.0 to 132.0° C. and theallowable range was very narrow as 1.0° C., and therefore, it wasdifficult to control the sealing temperature and defective products werelikely to be generated, resulting in low yield.

In the pliable plastic films of Comparative Examples 1 and 2, a blockingphenomenon in which inner faces of the container are fused with eachother, and deterioration of easy releasability due to an increase of thepeel strength of an easily releasable seal occurred after thesterilization treatment.

Examples 2 to 8

In the same manner as in Example 1, except for employing the layerconfiguration shown in Table 3 below, a pliable plastic film wasproduced and also a container (infusion solution bag) 10 shown in FIG. 1was produced using the film in the same manner as in Example 1.

TABLE 3 Upper columns: Kinds of plastics constituting layers Lowercolumns: Mixing ratios (weight ratios) of plastics First Rein- SecondSealing flexible forcing flexible Outermost layer layer layer layerlayer (30 μm) (90 μm) (20 μm) (90 μm) (20 μm) Example 2 PP1 + PP2 PP1 +PEE PP1 PP1 + PEE PP1 (95:5)  (60:40) (60:40) Example 3 PP1 + PP2 PP1 +PEE PP1 PP1 + PEE PP1 (90:10) (60:40) (60:40) Example 4 PP1 + PP2 PP1 +PEE PP1 PP1 + PEE PP1 (80:20) (60:40) (60:40) Example 5 PP1 + PP2 PP1 +PEE PP1 PP1 + PEE PP1 (70:30) (60:40) (60:40) Example 6 PP1 + PP2 PP1 +PEE PP2 PP1 + PEE PP1 (85:15) (60:40) (60:40) Example 7 PP1 + PP2 PP1 +PEE COP PP1 + PEE PP1 (85:15) (60:40) (60:40) Example 8 PP1 + PP4 PP1 +PEE PP1 PP1 + PEE PP1 + PP2 (85:15) (60:40) (60:40) (50:50)

With respect to the containers (infusion solution bags) 10 producedusing the pliable plastic films of Examples 2 to 8, the peel strength(N/15 mm) was measured while varying the sealing temperature at whichthe easily releasable sealed portion is formed, in the same manner as inExample 1. As a result, the allowable temperature ranges (° C.) of heatsealing, at which the peel strength of the easily releasable seal couldbe maintained within a range from 3.92 to 5.88 N/15 mm, were 2° C. ormore in Examples 2 to 8.

While the illustrative embodiments and examples of the present inventionare provided in the above description, such are for illustrative purposeonly and not to be construed restrictively. Modification and variationof the present invention which will be obvious to those skilled in theart are to be covered in the following claims.

The disclosure of Japanese patent application No. 2004-203831, filed onJul. 9, 2004, is incorporated herein by reference.

1. A pliable plastic film comprising a heat sealable sealing layer,wherein the sealing layer is made of a mixture of a propylene-α-olefinrandom copolymer having a crystalline melting point T_(m) of 135 to 145°C. and a polypropylene homopolymer having a crystalline melting pointT_(m) of higher than 160° C.
 2. The pliable plastic film according toclaim 1, wherein a content ratio of the polypropylene homopolymer isfrom 5 to 30% by weight based on the mixture.
 3. The pliable plasticfilm according to claim 1, wherein the polypropylene homopolymer has amelting point of more than 160° C. and not more than 170° C. and anisotactic pentad fraction of not less than 0.97.
 4. The pliable plasticfilm according to claim 2, wherein the polypropylene homopolymer has amelting point of more than 160° C. and not more than 170° C. and anisotactic pentad fraction of not less than 0.97.
 5. The pliable plasticfilm according claim 1, further comprising a layer containingpolypropylene formed on a surface of the sealing layer.
 6. The pliableplastic film according to claim 1, further comprising a first flexiblelayer formed on a surface of the sealing layer, a reinforcing layerformed on a surface of the first flexible layer, a second flexible layerformed on a surface of the reinforcing layer, and an outermost layerformed on a surface of the second flexible layer, wherein the firstflexible layer is made of a mixture of at least one kind of polymerselected from the group consisting of a propylene-α-olefin randomcopolymer, a propylene-α-olefin block copolymer and a syndiotacticpolypropylene, and an ethylene-α-olefin copolymer elastomer, and thecontent ratio of the ethylene-α-olefin copolymer elastomer is from 30 to50% by weight based on an entire of the first flexible layer, thereinforcing layer is made of at least one kind of polymer selected fromthe group consisting of a polypropylene homopolymer, apropylene-α-olefin random copolymer, a propylene-α-olefin blockcopolymer and a cyclo olefin polymer, the second flexible layer is madeof a mixture of at least one kind of polymer selected from the groupconsisting of a propylene-α-olefin random copolymer, apropylene-α-olefin block copolymer and a syndiotactic polypropylene, andan ethylene-α-olefin copolymer elastomer, and the content ratio of theethylene-α-olefin copolymer elastomer is from 30 to 50% by weight basedon an entire of the second flexible layer, and the outermost layer ismade of at least one kind of polymer selected from the group consistingof a polypropylene homopolymer, a propylene-α-olefin random copolymerand a propylene-α-olefin block copolymer.
 7. The pliable plastic filmaccording to claim 6, wherein the thicknesses of the first flexiblelayer and the second flexible layer respectively account for 30 to 40%of an entire of the film thickness.
 8. A container formed by using apliable plastic film comprising a heat sealable sealing layer, thesealing layer being made of a mixture of a propylene-α-olefin randomcopolymer having a crystalline melting point T_(m) of 135 to 145° C. anda polypropylene homopolymer having a crystalline melting point T_(m) ofhigher than 160° C., the container being provided with a sealed portionformed by heat sealing peripheral portions of the pliable plastic filmsin the state where the sealing layers thereof face with each other. 9.The container according to claim 8, which is provided with an easilyreleasable sealed portion having a smaller peel strength than that ofthe sealed portion, and is also provided with a plurality of chamberspartitioned with the sealed portion and the easily releasable sealedportion.
 10. The container according to claim 9, wherein the easilyreleasable sealed portion is heat sealed at a temperature which ishigher than a crystalline melting point T_(m) of the propylene-α-olefinrandom copolymer having a crystalline melting point T_(m) of 135 to 145°C. and is lower than a crystalline melting point T_(m) of thepolypropylene homopolymer having a crystalline melting point T_(m) ofhigher than 160° C.
 11. The container according to claim 8, which issubjected to a sterilization treatment at 121° C.